There could be. Fanfiction allows for a wide range of interpretations and alternate storylines. But it's a really extreme and disturbing concept considering the bonds that Naruto, Sakura, and Sasuke share in the official story. It would be a very different take on the characters, and most fans who love the original story would probably find it hard to accept.
This fanfiction changes the power balance within Konoha. Sakura was growing to be a capable kunoichi. Her death would mean a loss of potential power and knowledge for Konoha. Also, it could lead to a rift between Sasuke and the village. Instead of being a potential ally or a wayward ninja, he becomes a murderer, and Konoha would have to deal with him differently.
One possible motive could be that Sasuke has been consumed by his thirst for power. In the Naruto universe, Sasuke has often been shown to be willing to sacrifice a lot for power. In this fanfiction set in the Wave arc, perhaps he sees Sakura as an obstacle to his pursuit of power, either because she tries to stop him from following a dark path or he believes she will hold him back in some way.
Sakura might be in shock. She probably couldn't believe that Sasuke, someone she cares about deeply, would try to kill her. So she could be frozen in place for a moment, unable to react immediately.
One possible reason could be that Sasuke was under some kind of mind - control or dark influence at that moment. Maybe he was influenced by an enemy's jutsu that made him lose his sense of self and turn on Sakura.
A possible motive could be a creative exploration of the 'what - if' scenarios. Maybe the writer wants to see how the story would unfold if Sasuke completely lost his way. Another motive could be to create a sense of high - stakes drama. Since Sakura is an important character, her death at Sasuke's hands would be a huge shock.
One possible reason could be a sudden and extreme corruption of Naruto's character. Maybe he is influenced by some dark and powerful force that makes him turn against his friends. Another reason might be a misinterpretation of a prophecy or some kind of mind - control situation.
One possible motive could be that Sakura is brainwashed. Maybe an enemy uses some kind of mind - control jutsu on her and she becomes a puppet to kill Sasuke. Another could be extreme jealousy. If she felt that Sasuke was slipping away from her in some way, in a very dark and twisted version of the story, it could lead to her killing him.
It could be because of a dark power corrupting Sasuke. Maybe an ancient evil force takes over him and makes him see Sakura as an enemy. In some fanfics, this kind of external influence can completely change a character's actions. Also, it might be related to Sasuke's pursuit of power. If he believes Sakura is standing in the way of his ultimate power - seeking goal, he could be driven to kill her.
It's relatively rare. In the Naruto fandom, Naruto, Sasuke, and Sakura are central characters with complex relationships. Naruto and Sasuke are rivals but also friends, and Sakura is part of their team. Most fanfictions focus on their growth, friendship, or romantic relationships. Killing off two such important characters goes against the general positive and growth - oriented themes that many fans prefer.